A major Turkish city is turning into a war zone

Children walk past by damaged buildings in Sur district, which is partially under curfew, in the Kurdish-dominated southeastern city of Diyarbakir, Turkey on February 19, 2016. Sertac Kayar/Reuters Turkey has struggled with the consequences of the destructive civil war in neighboring Syria. Now, the Turkish army is shelling the ancient center of one of the country's major cities, partially as a result of how the Syria conflict has impacted Turkey's long-running Kurdish insurgency.

Ankara's stance against the regime of Syrian president Bashar al-Assad has put it at odds with both Iran and Russia.

Moreover, the Russian intervention in Syria brought Turkey and Russia to the brink of open conflict this past November when Turkey shot down a Russian plane that had allegedly strayed into the country's airspace.

But the Syria conflict's real danger to Turkey is playing out within its own borders, particularly in a city of nearly 1 million people on the banks of the Tigris River in Turkey's southeast.

Diyarbakir includes a UNESCO-listed historic quarter surrounded by nearly 3.5 miles of thick Roman-era city walls. It's also one of the region's largest majority-Kurdish cities.

Today, the old city's Sur district is a warzone, with militants affiliates with the autonomy-seeking Kurdistan Worker's Party (PKK) fighting the Turkish military.

Location of Diyarbakir Google Maps The fighting is the latest chapter in an over 30-year-old conflict between the Turkish state and the country's historically marginalized Kurdish minority.

As Deutsche Welle reported in January, thousands of people have fled the old city area, where water and electricity had been cut off.

Turkey's Human Rights Association reported that nearly 200 civilians had been killed in the fighting up to that point, according to Deutsche Welle.

On Thursday, Mahmut Bozarslan, a Kurdish journalist based in the city, told Business Insider by email that shelling of the old city is ongoing, and that "heavy shelling" occurred over the weekend. Bozarslan estimated that over 50,000 people had fled the old city to other parts of Diyarbakir since the fighting escalated in December.

Inside the territory of a NATO member state, the government is turning its heavy weaponry against an insurgent group that has established a persistent foothold within a major city.

The situation in Diyarbakir threatens to descend into protracted urban warfare. It's currently winter in southeastern Turkey, but observers expect combat to intensify. "It depends on PKK's decision for spring," Bozarslan told Business Insider by email. "In my view, it will get worse."

Residents carry their belongings as they flee from Sur district, which is partially under curfew, in the Kurdish-dominated southeastern city of Diyarbakir, Turkey on January 27, 2016. Sertac Kayar/Reuters The renewed insurgency in Diyarbakir, and throughout southeastern Turkey, is exacerbated by the conflict in neighboring Syria.

In Syria's Kurdish regions, the People's Protection Units (YPG) militias have proven to be the US's most effective ground-level partners in the fight against ISIS in the country. Even if the YPG is more open to working with the Assad regime than other non-government forces and even tolerates the presence of regime military within territory they control, they've also carved out their own autonomous sphere in Kurdish-majority areas in Syria. At the moment, the regime is incapable of regaining full control.

Buildings which were damaged during the security operations and clashes between Turkish security forces and Kurdish militants, are pictured in Sur district of Diyarbakir, Turkey on February 11, 2016. Sertac Kayar/Reuters But the PYD is the Syrian affiliate of the PKK, giving them operational ties to a US and EU-listed terror group that the Turkish government considers to be one of the primary threats to the country's security.

Syrian Kurds' new regional prominence and international prestige has upset a delicate ethnic balance in Turkey, site of a PKK insurgency that's lasted for three decades, a conflict that has killed some 40,000 people.

Reuters Kurdish groups in Syria believe that political and battlefield momentum is on their side. Meanwhile, an increasingly autocratic Turkish state fears the PKK now has a Syrian safe-haven, along with US political backing and military support.

At the moment, ISIS, the Syrian civil war, and the Turkish government's anxieties all mean that armed conflict will continue inside of a key NATO state — with Diyarbakir becoming yet another front in a region-wide conflagration.